Electrically heated distributor cap

ABSTRACT

Continuous and efficient operation of spark ignition distributor caps under conditions of high humidity is promoted by heating the space enclosed within the cap. Such heating inhibits high humidity and moisture formation on the cap interior. The heating means can be located either outside the cap or in the cap interior. An exemplary heating means is an electrical heating element, and it can be positioned, for example, interiorly to the cap exterior surface. Additionally, a thermostatic control can be employed to maintain a desired temperature range in the cap interior.

United States Patent I Inventors Raymond J. Guth Rochester; John T. Elle, East Bloomfield, both of N.Y. Appl. No. 9,517 Filed Feb. 9, 1970 Patented Jan. 4, 1972 Assignee Dennis M. DeLeo Webster, N.Y. a part interest ELECTRICALLY HEATED DISTRIBUTOR CAP 4 Claims, 4 Drawing Figs.

US. Cl 219/209, 123/1465 R, 219/202 Int. Cl 1105b 1/00 Field of Search 219/200,

References Ci ted UNITED STATES PATENTS 2,660,656 11/1953 Wilkie Primary Examiner-C. L. Albritton Anorney-Dennis M. DeLeo ABSTRACT: Continuous and efficient operation of spark ignition distributor caps under conditions of high humidity is promoted by heating the space enclosed within the cap. Such heating inhibits high humidity and moisture formation on the cap interior. The heating means can be located either outside the cap or in the cap interior. An exemplary heating means is an electrical heating element, and it can be positioned, for example, interiorly to the cap exterior surface. Additionally, a thermostatic control can be employed to maintain a desired temperature range in the cap interior.

PATENTEDJAN 41972 7 31 632.965

F VENTORS -LF- RA MD J. GUTH JOHN T. ELLE ELECTRICALLY HEATED DISTRIBUTOR CAP This invention relates to internal combustion engine spark distributor caps and particularly to distributor caps having a heating means to inhibit moisture formation on the cap interior surface and within the cap, thereby preventing failure of the cap during high-humidity engine operation.

There has been a long existent and bothersome problem of difficult engine starting during rainy spells or under high-humidity operating conditions, which problem has been found to center in the ignition distributor. This problem has been aggravated in certain vehicle installations due to the fact that the distributor location in the vehicle engine compartment may have very little road water splash protection and/or air inlet apertures or ducting for the engine compartment tend to pass large volumes of moisture-saturated air around the distributor unit such that moisture is deposited on the exterior of and introduced to the interior of the distributor cap.

it has been determined that a major problem associated with high-humidity distributor-operating conditions is conductivity of the cap interior surface. Such conductivity is promoted both by the inherent low electrical resistance of an aqueous frlm present on the cap interior surface and by the deterioration of that surface, resulting in an uneven sparking operation and ultimate failure of desired spark action.

Distributor cap conductivity resulting from deterioration of the cap interior surface is especially promoted by the presence of moisture-laden air within the cap during operating periods. At such times, undesirable electrical shorting that can occur (i.e., in moist atmosphere) between closely positioned hightension contact studs stimulates the formation of a conductive film or path.

Additionally, such conductive pathways decrease the hydrophobicity of the cap interior surface. This in turn promotes more frequent electrical shorting and an acceleration of the cycle of degradation, spark interruption and ultimate spark failure.

More specifically, the high-voltage sparking which conventionally occurs within the distributor cap causes the formation of nitrogen oxides produced as chemical decomposition products of'air within the cap. These oxides, in the presence of water, form nitric acid which, in combination with the ozone also formed inside the cap by sparking action, promotes deterioration of the phenolic or other insulating resin cap material. Nitric acid can also chemically react with the metallic high-tension contact studs to produce conductive metal nitrate salt deposits on the interior cap surface. The deterioration of the cap material decreases its hydrophobicity and renders the cap interior surface more susceptible to the formation thereon of a moist film or path which, as noted herein, promotes deleterious electrical shorting between spark terminals.

The above discussion indicates that distributor cap failure is precipitatedboth by the increased hydrofelicity of a chemically degradedcap interior surface and by the formation of highly conductive metal nitrate salts within the cap. Each of these failure aspects is directly related to the presence of high humidity or moisture within the cap. Once a conducting path is established, the formation of even more highly conducting carbon tracks or metal salt paths is inevitable and leads tothe ultimate complete operating failure of the cap. The carbon tracks or paths are formed by spark-induced pyrolysis along portions of the cap interior surface traversed by short-circuited spark discharges. The presence of conducting metal salts merely hastens complete cap failure.

To overcome the above-mentioned difficulties, it has been suggested that distributor caps can be fabricated from comparatively chemically inert thermoplastic resins; it has likewise been proposed that the distributor caps can be ventilated to permit egress of trapped moisture to the atmosphere; electrically insulating, substantially inert hydrophobic resinous coatings have also been proposed in order to mitigate against the short circuit promoting characteristics of the aforementioned high-humidity conditions. No presently available method or apparatus, however, has functioned to promote a condition within the distributor cap which inhibits the formation of moisture or, if present, promotes its removal. Known methods have been directed towards diminishing the rate of moisture induced degradation rather than towards the elimination of the moisture itself.

Accordingly, it is an object of this invention to provide a novel spark ignition distributor cap.

It is another object of this invention to provide a new spark ignition distributor cap which inhibits the formation of moisture within the cap.

Yet an additional object of the instant invention is to provide a novel spark ignition distributor cap including a heating means.

Still another object of the present invention is to provide a new spark ignition distributor cap including an electrical heating means to inhibit the formation of moisture within the cap and on the cap interior surface.

An additional object of this invention is to provide a novel spark ignition distributor cap including switchable electrical heating means to inhibit the formation of moisture within the cap and on the cap interior surface.

Still another object of the present invention is-to provide a process for inhibiting the formation of moisture within a spark ignition distributor cap.

The objects of this invention are accomplished with a process for promoting spark ignition under conditions of high humidity of moisture formation on either the interior surface of a spark ignition distributor cap or in the space enclosed within the cap interior surface, which process involves heating the cap interior surface and the space enclosed within that interior surface to inhibit or remove said conditions of high humidity or moistureformation. In another aspect, the objects of the present invention are accomplished with an improved spark ignition distributor cap formed from an electrically insulating resin material and having on the exterior surface spaced-apart high-tension terminals and on the interior surface spaced-apart high-tensioncontact studs, the terminals and contact studs being respectively electrically connected through the cap, wherein the improvement includes having, as a means of restraining and inhibiting the formation or existence of moisture on the cap interior surface and within the cap, a heating means positioned in the cap interiorly to the cap exterior surface. 1

The process of heating the cap interior surface to inhibit or restrain the formation of a high-humidity environment, including condensed moisture, either on the cap interior surface or in the enclosed gaseous components, e.g., air, can be accomplished conveniently by a variety of means. In one aspect, ex temally heated air can be directed-through or around the distributor cap in any suitable fashion, such as through an orifice integral to the distributor cap, to cause heated airto be maintained in the region enclosedwithin the distributor cap. Such heated air can be transported to the cap interior region by force-feed means, such as a blower mechanism, or it can be transported by means of convection. Advantageously, a tube or other ducting means is used to maintain a desired flow path for directing the heated air into the cap interior region. A varied range of external heating sources can be used to heat the air intended for introduction into the cap interior region.

It is preferable that the air is heated to at least about 50 C. in order to facilitate the evacuation of or inhibit the formation of moisture within the cap. Air temperatures significantly in excess of 120 C. are not generally required unless a large quantity of moisture must be dissipated or a high-humidity operating environment is maintained over an extended time Any technique capable of effecting the generation of heat within the distributor cap can be employed. A particularly useful method, however, is the utilization of an electrical heating means since it can provide a source of heat without requiring either bulky or complex apparatus. Moreover, electrical heating components can be efficiently and rapidly switched in or out of operation either manually or automatically, such as by a thermostatic control, e.g., a bimetal element or a thermocouple.

- Advantageous heating components include electrical resistance heaters such as coil elements and linear elements, and they can be arranged in a wide variety of configurations to achieve the optimum heat generation for particular distributor caps or operating environments. The heating element can be desirably encapsulated within the electrically insulating resin material which forms the distributor cap, with tenninals suitable for electrical connection to supplemental circuitry extending from the cap exterior surface. Alternatively, the heating source can be positioned into a recess in the cap interior surface and electrical connection to exterior circuitry can be made, for example, by suitable terminals, such as those described elsewhere herein, integral to the cap wall. With such an arrangement, heat is not required to penetrate a substantial amount of insulating resin and efficiency is heightened. A heating means located within the distributor cap, and advantageously at a low position on the cap wall, promotes convection currents which carry the heat to all regions enclosed by the cap interior surface. If desired, small exhaust vents can be used, e.g., at the upper portion of the cap, to provide an outlet for moisture vapor and also to design a particular convectional airflow within the cap. A grille or other perforated or otherwise substantially open shield can be placed over the heating element for safety purposes. Desirably, such a shield is composed of an electrically insulating material since the presence of electrical conductors other than the spark terminals can promote deleterious arcing within the cap. In yet another arrangement, the heating means can be positioned on the cap interior surface without the use of a groove or other recess into which the heating element can be positioned.

Electrical heating elements like those described herein either can be wired for continuous operation or can be actuated by a switching mechanism. The choice of a particular switch means is susceptible of extensive variation, but two types of switch apparatus, i.e., manual and thermostatic, are particularly convenient. With the use of a manual switch, the heating mode can be selected according to the desire of an operator when high-humidity conditions are encountered. The switch can be positioned, for example, in a location remote from the distributor cap but conveniently accessible to an operator. A thermostatic switch apparatus can be designed to maintain a desired temperature within the distributor cap. The particular selected temperature range can be widely varied, but it can be selected for optimum inhibition of moisture formation in a particular operating environment. With thermostatic switching means, the temperature selector can be located such that an operator can continuously vary the distributor cap interior heat.

The above and other features and objects of the present invention will be increasingly apparent having reference to the preceding and following specification and claims taken in conjunction with the accompanying drawing in which:

FIG. 1 is a top plan view of a distributor cap for an eightcylinder spark-ignition internal combustion engine;

FIG. 2 is a sectional elevational view taken along the line of and in the direction of the arrows 22 of FIG. 1;

FIG. 3 is a fragmentary sectional elevational view taken along the line of and in the direction of' the arrows 3-3 of FIG. 1; and

FIG. 4 is a fragmentary sectional elevational view taken along the line of and in the direction of the arrows 4-4 of FIG. 1.

Referring now to the drawing, wherein like numbers indicate similar parts, the spark-ignition distributor cap illustrated in FIG. 1 includes a cup-shaped cap element 1 formed from an electrically insulating, advantageously hydrophobic, resinous or plastic material such as a phenol-formaldehyde resin, a polyester, an acrylic resin, a polyamide resin, e.g., a nylon, or the like resin material. The closed bottom end 2 of cup 1 has a centrally positioned tower 3 projecting outwardly therefrom. This central tower 3 has seated therein and projecting through the cup bottom 2 a tubular contact terminal 4. Terminal 4 is adapted to receive one end of a wire conductor element that is adapted to be connected to the high-tension winding of an ignition coil (not shown). Extending about the periphery of the cup bottom 2 and projecting outwardly therefrom are eight circumferentially spaced towers 5 that each seat a tubular contact terminal 6. Extending from the periphery of the cap 1 are electrical connector terminals 16 adapted to make an electrical connection with a heating means contained interiorly to the cap exterior surface.

Looking now at FIG. 2, the lower ends 7 of the terminals 6 project through the bottom 2 of the cup 1 to provide contact studs for intermittent spark connection with contact 8 of distributor rotor 9. Rotor 9 is carried by rotor shaft 10 that is drivingly connected to the associated engine camshaft (not shown). The terminals 6 are each adapted to receive a wire conductor that is connected to one of the spark plugs of the associated engine. Also as shown in FIG. 2, the wall of cap element 1 exhibits, on the inner surface 11, a circumferential recess or depression 12 adapted to receive a heating element 13. The element 13 is covered by a protective, substantially open grille l4 and is attached to grille 14 for purposes of stability by insulating spacers 15. Grille 14 is demountably mounted to the cap inner surface 1 1. Also illustrated in FIG. 2 is an electrical connector terminal 16 which permits the wiring of an electrical supply source (not shown) to heating element 13 through the wall of cap element 1. Two separate electrical connections are required to provide a complete electrical circuit.

It will be understood by skilled persons that a wide variety of useful heating elements can be affixed to a nonrecessed cap inner surface, that the grille shape, composition and method of mounting of the grille are all susceptible of wide interchange, that the electrical terminal or connector can be affixed to the cap by rivets, snap fasteners, etc., and that the choice of a particular connector is widely variable, e.g., a pushon blade-type connectors, plug-in connectors or the like. The particular choice of materials and a specific operative mode is dependent upon the design objectives of the distributor apparatus and the environment in which it will be used, e.g., road vehicle, stationary engine, aircraft, marine, subterranean (mining vehicle or machine) or the like.

As shown in FIG. 3, the depression 12 is continuous and circumferential along the cap inner surface 11, and the heating element 13 is positioned between the cap inner surface 11 and the protective grille 14. The open configuration of the grille l4 permits airflow over and around heating element 13 to establish convection currents which promote heating of the area enclosed by the cap element 1.

Referring now to FIG. 4, heating element 13 is connected to an electrical connector terminal 16 through a bimetallic thermostatic control 17 which makes or breaks the heating circuit at contacts 18. As an alternative (not shown) a third electrical terminal can be wired directly to the contacts 18 to bypass the thermal control. In that event, by merely changing a wire from one terminal to another, the thermostatic control can be used or bypassed as desired. By use of a switch, even the necessity for changing electrical connections can be avoided.

The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

We claim:

1. In a spark-ignition distributor cap formed from an electrically insulating resin material and having on the exterior surface thereof spaced-apart high-tension terminals and on the wherein said cap also comprises a substantially open electrically insulating shield means over said heating means.

3. A spark ignition distributor cap as described in claim 1 where said heating means also includes an on-off switching means.

4. A spark ignition distributor cap as described in claim 1 wherein said heating means is positioned in a circumferential recess located at a low position on said interior surface.

I! i i I 

1. In a spark-ignition distributor cap formed from an electrically insulating resin material and having on the exterior surface thereof spaced-apart high-tension terminals and on the interior surface thereof spaced-apart high-tension contact studs, said terminals and contact studs being respectively electrically connected through said cap, the improvement which comprises having, as a means of inhibiting the formation of moisture of said interior surface and within the cap, an electrical heating means in said cap interiorly to said exterior surface, said heating means being arranged circumferentially at a low position in said cap.
 2. A spark ignition distributor cap as described in claim 1 wherein said cap also comprises a substantially open electrically insulating shield means over said heating means.
 3. A spark ignition distributor cap as described in claim 1 wherein said heating means also includes an on-off switching means.
 4. A spark ignition distributor cap as described in claim 1 wherein said heating means is positioned in a circumferential recess located at a low position on said interior surface. 